Antisense inhibition of gene expression, mediated either by plasmid generated antisense RNA or exogenously added synthetic single stranded DNA, is now a widely used experimental technique (41, 42). The use of this technology in clinical medicine is also receiving intense investigation (43, 44, 45, 46). However, as our understanding of the intracellular fate of exogenously added synthetic oligodeoxynucleotides (ODNs) expands, it is becoming clear that these molecules can participate in non-antisense mediated phenomena (34). Among the most unexpected of these is the sequence-specific direct interaction of ODNs with proteins. Such so-called "aptamer" effects are presumably mediated by the formation of ODN-protein complexes whose specificity is determined by both ODN sequence and protein structure.
Protein tyrosine kinases (PTKs) transfer the gamma phosphate of either ATP or GTP to specific tyrosine residues of acceptor proteins (1). These enzymes and their substrate proteins are important mediators of cellular signal transduction and their aberrant function is frequently associated with deregulated growth and neoplasia (2-8). In fact, the first oncogenic protein characterized, isolated from the transforming retrovirus Rous sarcoma virus, was the PTK src (9). Many of the subsequently discovered oncogenes are also PTKs. PTK inhibitors, therefore, may represent an important class of anti-neoplastic agents (10-12). The majority of PTK inhibitors consist of agents that either inhibit nucleotide or tyrosine containing substrate binding, while the remainder effect catalysis by other means (13-14). Since a high degree of homology exists among the nucleotide binding domains of many ATP-utilizing enzymes, existing inhibitors of nucleotide binding lack specificity for particular PTKs, and in some cases cannot distinguish between PTKs and other kinases.
Chronic myelogenous leukemia (CML) cells contain a unique chromosomal translocation, the Philadelphia chromosome, resulting in the expression of a novel PTK, the p210.sup.bcr-abl protein (15). This PTK has been directly implicated in the ontogeny and progression of CML (16).
Direct interaction of an oligo-deoxynucleotide (ODN) with a protein has been described (33). Although several `aptamer` effects have been reported in the literature, the rules governing these interactions are not at all clearly understood (33-37). Techniques have been developed to optimize the process of aptameric ODN selection (35). Such an approach has led to the identification of a specific ODN that inhibits thrombin function (33). Until the present invention, ODNs having a specificity for a particular PTK have not been described in the literature.